In microorganisms belonging to the genus Escherichia and the like, L-glutamine serves not only as a substrate for protein synthesis, but also as a nitrogen-supplying substrate in the biosynthesis of purine and pyrimidine nucleic acids and amino acids such as L-arginine, L-histidine, L-tryptophan and L-asparagine.
On the other hand, L-glutamine biosynthesis is catalyzed by glutamine synthetase (GS) encoded by the glnA gene and it is known that GS activity is subject to very strict and complicated regulation. That is, GS is negatively controlled by adenylylation. Such adenylylation and deadenylylation are catalyzed by glutamine-synthetase adenylyltransferase (hereinafter referred to as GlnE protein) encoded by the glnE gene, and the direction of catalysis is determined by PII regulatory protein for glutamine synthetase (hereinafter referred to as GlnB protein) encoded by the glnB gene. When the GlnB protein is uridylylated, it promotes deadenylylation of GS by the GlnE protein, and on the contrary, when the GlnB protein is not uridylylated, it promotes adenylylation of GS by the GlnE protein. The uridylylation and deuridylylation of the GlnB protein are determined by a protein encoded by the glnD gene. As L-glutamine promotes deuridylylation, GS is adenylylated to cause a lowering of GS activity, leading to regulation suppressing L-glutamine synthesis. On the other hand, 2-oxoglutaric acid promotes uridylylation of the GlnB protein, whereby L-glutamine synthesis is promoted according to the scheme opposite to the above (non-patent publication Nos. 1 and 2).
Attempts have been made to produce L-glutamine by fermentation by deregulating the above-described complicated mechanism. In patent publication No. 1, it is described that Escherichia coli which forms and accumulates L-glutamine was obtained by modifying GS so that its adenylylation site shall not be adenylylated and by enhancement of the expression of the glnA gene, but the L-glutamine production by the microorganism is only 1.3 g/l.
Further, the following microorganisms are known: glutamine-producing strains such as Corynebacterium plutamicum having glnE gene deletion (patent publication No. 2) and Corynebacterium plutamicum in which the glnA gene is modified and the expression of the gdh gene is enhanced (patent publication No. 2); L-arginine-producing strains such as Escherichia coli into which the ghA gene was introduced (patent publication No. 3); L-tryptophan-producing strains such as Escherichia coli into which the tryptophan operon, aroG gene and serA gene were introduced (patent publication No. 4); L-histidine-producing strains such as Escherichia coli conferred aminoquinoline resistance (patent publication No. 5); and nucleic acid-producing strains such as 5′-inosinic acid-producing Escherichia coli in which the purA, deoD, purR, add, gsk, edd, xapA, ushA and aph genes are deleted and the expression of the desensitized purF gene is enhanced (patent publication No. 6) and 5′-guanylic acid-producing Escherichia coli in which the purA, deoD, purR, add, gsk, edd, xapA, ushA and aph genes are deleted and the expression of the desensitized purF gene and the guaAB gene is enhanced (patent publication No. 6). However, there has been no report on a microorganism belonging to the genus Escherichia in which the activities of the GlnE protein and the GlnB protein are reduced or lost and which has the ability to form and accumulate L-glutamine or a substance biosynthesized utilizing nitrogen supplied by L-glutamine, and a process for producing L-glutamine or the substance using the microorganism.    Non-patent publication No. 1:
E. coli and Salmonella, Second Edition (1996)    Non-patent publication No. 2:
FEMS Microb. Lett., 201, 91-98 (2001)    Patent publication No. 1:
Japanese Published Unexamined Patent Application No. 164297/03    Patent publication No. 2:
Japanese Published Unexamined Patent Application No. 300887/02    Patent publication No. 3:
Japanese Published Unexamined Patent Application No. 5693/82    Patent publication No. 4:
U.S. Pat. No. 5,939,295    Patent publication No. 5:
Japanese Published. Unexamined Patent Application No. 86998/01    Patent publication No. 6:
Japanese Published Unexamined Patent Application No. 355087/02